UDF for evaporation rate and mass fraction

Faravi Ahmed · June 10, 2020, 14:39

Hi,

I am a beginner in Ansys and C programming and working on water droplet evaporation in the air with the VOF model. I am kind of stuck writing the UDF at the interface for evaporation rate and mass/mole fraction of vapor.

It would be a great help if anyone helps me with this. Any suggestion/reference would be highly appreciated on how I can develop my knowledge on droplet evaporation.

# I went through the UDF manual several times but could not find any proper guidelines on how to write the functions.

# Is there any default model for evaporation rate and mass/mole fraction in UDF?

Thanks in advance.

Regards,
Faravi

AlexanderZ · June 10, 2020, 21:37

https://www.cfd-online.com/Forums/se...archid=6830821

vinerm · June 15, 2020, 04:06

You don't need a UDF. Fluent has in-built models for this. You can either use Lee or Thermal Phase Change Model. With VOF, only Lee is available.

Faravi Ahmed · June 15, 2020, 11:50

Thank you so much for your reply.

#I have another question regarding mass fraction and mole fraction at the interface. Do I have to use UDF for it or Ansys VOF model will automatically use this?

Regards,
Faravi

Faravi Ahmed · June 15, 2020, 11:57

Hi Vinerm,

Thanks for your reply.

I was wondering do I have to use UDF for mass fraction or mole fraction at the interface or Ansys Vof model will implement this automatically?

Regards,
Faravi

vinerm · June 15, 2020, 15:25

No UDF is needed. Inbuilt model will suffice. Enable mass transfer and select Evaporation-Condensation model.

Faravi Ahmed · June 17, 2020, 12:15

Thanks again Vinerm for your reply.

June 10, 2020, 14:39	UDF for evaporation rate and mass fraction	#1
Faravi Ahmed New Member TX Join Date: Jun 2020 Posts: 4 Rep Power: 5	Hi, I am a beginner in Ansys and C programming and working on water droplet evaporation in the air with the VOF model. I am kind of stuck writing the UDF at the interface for evaporation rate and mass/mole fraction of vapor. It would be a great help if anyone helps me with this. Any suggestion/reference would be highly appreciated on how I can develop my knowledge on droplet evaporation. # I went through the UDF manual several times but could not find any proper guidelines on how to write the functions. # Is there any default model for evaporation rate and mass/mole fraction in UDF? Thanks in advance. Regards, Faravi Last edited by Faravi Ahmed; June 10, 2020 at 17:39.

June 10, 2020, 21:37		#2
AlexanderZ Senior Member Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34	https://www.cfd-online.com/Forums/se...archid=6830821 __________________ best regards ****************************** press LIKE if this message was helpful

June 15, 2020, 04:06	Evaporation of Droplet	#3
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 35	You don't need a UDF. Fluent has in-built models for this. You can either use Lee or Thermal Phase Change Model. With VOF, only Lee is available. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

June 15, 2020, 15:25	Mass Transfer	#6
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 35	No UDF is needed. Inbuilt model will suffice. Enable mass transfer and select Evaporation-Condensation model. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

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June 15, 2020, 11:50		#4
Faravi Ahmed New Member TX Join Date: Jun 2020 Posts: 4 Rep Power: 5	Thank you so much for your reply. #I have another question regarding mass fraction and mole fraction at the interface. Do I have to use UDF for it or Ansys VOF model will automatically use this? Regards, Faravi

June 15, 2020, 11:57		#5
Faravi Ahmed New Member TX Join Date: Jun 2020 Posts: 4 Rep Power: 5	Hi Vinerm, Thanks for your reply. I was wondering do I have to use UDF for mass fraction or mole fraction at the interface or Ansys Vof model will implement this automatically? Regards, Faravi

June 17, 2020, 12:15		#7
Faravi Ahmed New Member TX Join Date: Jun 2020 Posts: 4 Rep Power: 5	Thanks again Vinerm for your reply.